U.S. patent number 10,737,503 [Application Number 16/104,768] was granted by the patent office on 2020-08-11 for fluid circulation apparatus and fluid ejection apparatus.
This patent grant is currently assigned to TOSHIBA TEC KABUSHIKI KAISHA. The grantee listed for this patent is TOSHIBA TEC KABUSHIKI KAISHA. Invention is credited to Taiki Goto, Kazuhiro Hara.
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United States Patent |
10,737,503 |
Hara , et al. |
August 11, 2020 |
Fluid circulation apparatus and fluid ejection apparatus
Abstract
According to one embodiment, a fluid circulation apparatus
includes a first tank to store fluid to be supplied to a fluid
ejection head, a circulation path including a first flow path
portion to provide fluid from the first tank to a supply port of
the fluid ejection head, and a second flow path portion to return
fluid from a collection port of the fluid ejection head to the
first tank, a bypass flow path that connects the supply port to the
collection port outside of the fluid ejection head, and a buffer
tank in the bypass flow path.
Inventors: |
Hara; Kazuhiro (Numazu
Shizuoka, JP), Goto; Taiki (Mishima Shizuoka,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TOSHIBA TEC KABUSHIKI KAISHA |
Tokyo |
N/A |
JP |
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|
Assignee: |
TOSHIBA TEC KABUSHIKI KAISHA
(Tokyo, JP)
|
Family
ID: |
63556224 |
Appl.
No.: |
16/104,768 |
Filed: |
August 17, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190092035 A1 |
Mar 28, 2019 |
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Foreign Application Priority Data
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Sep 25, 2017 [JP] |
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2017-183721 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B41J
2/17596 (20130101); B41J 2/175 (20130101); B41J
2/17556 (20130101); B41J 2/17566 (20130101); B41J
2/19 (20130101); B41J 2/18 (20130101) |
Current International
Class: |
B41J
2/175 (20060101); B41J 2/19 (20060101); B41J
2/18 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2977210 |
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Jan 2016 |
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EP |
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3339039 |
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Jun 2018 |
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EP |
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2014-097619 |
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May 2014 |
|
JP |
|
2016-010786 |
|
Jan 2016 |
|
JP |
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2016-221817 |
|
Dec 2016 |
|
JP |
|
Other References
Extended European Search Report dated Feb. 13, 2019, mailed in
counterpart European Application No. 18193498.5, 9 pages. cited by
applicant .
U.S. Appl. No. 16/104,735, filed Aug. 17, 2018. cited by
applicant.
|
Primary Examiner: Lebron; Jannelle M
Attorney, Agent or Firm: Kim & Stewart LLP
Claims
What is claimed is:
1. A fluid circulation apparatus, comprising: a first tank to store
fluid to be supplied to a fluid ejection head; a circulation path
including a first flow path portion to provide fluid from the first
tank to a supply port of the fluid ejection head, and a second flow
path portion to return fluid from a collection port of the fluid
ejection head to the first tank; a bypass flow path that connects
the supply port to the collection port outside of the fluid
ejection head; a buffer tank in the bypass flow path; and an
opening/closing valve connected to an air chamber of the buffer
tank and configured to selectively open the air chamber to the
atmosphere.
2. The fluid circulation apparatus according to claim 1, wherein
the buffer tank has a flow path cross-sectional area that is larger
than a flow path cross-sectional area of the bypass flow path
between the buffer tank and at least one of the supply port and the
collection port.
3. The fluid circulation apparatus according to claim 2, wherein
the buffer tank has a deformable outer wall.
4. The fluid circulation apparatus according to claim 1, further
comprising: a first pump in the circulation path between the supply
port and the first tank, the first pump being configured to send
the fluid from the first tank toward the fluid ejection head; a
second pump in the circulation path between the collection port and
the first tank, the second pump being configured to send fluid from
the fluid ejection head toward the first tank; a pressure sensor
configured to detect pressure of the circulation path; and a
processor configured to adjust fluid output rates of the first pump
and the second pump based on the pressure of the circulation
path.
5. The fluid circulation apparatus according to claim 1, further
comprising: a first pump in the circulation path between the supply
port and the first tank, the first pump being configured to send
the fluid from the first tank toward the fluid ejection head; a
second pump in the circulation path between the collection port and
the first tank, the second pump being configured to send fluid from
the fluid ejection head toward the first tank; a pressure sensor
configured to detect pressure of the bypass flow path; and a
processor configured to adjust fluid output rates of the first pump
and the second pump based on the pressure of the bypass flow path
as detected by the pressure sensor.
6. The fluid circulation apparatus according to claim 1, wherein
the bypass flow path comprises a first bypass flow path portion
fluidly connecting the first flow path portion to the buffer tank
and a second bypass flow path portion fluidly connecting the buffer
tank to the second flow path portion, and the first bypass flow
path portion and the second bypass flow path portion are identical
to each other in length and a flow path cross-sectional area that
is less than a flow path cross-sectional area of the circulation
path.
7. A fluid ejection apparatus, comprising: a fluid ejection head
having a nozzle; a first tank to store fluid to be supplied to the
fluid ejection head; a circulation path including a first flow path
portion to provide fluid from the first tank to a supply port of
the fluid ejection head, and a second flow path portion to return
fluid from a collection port of the fluid ejection head to the
first tank; a bypass flow path that fluidly connects the first flow
path portion to second flow path portion; a buffer tank in the
bypass flow path; and an opening/closing valve connected to an air
chamber of the buffer tank and configured to selectively open the
air chamber to the atmosphere.
8. The fluid ejection apparatus according to claim 7, wherein the
buffer tank has a flow path cross-sectional area that is larger
than a flow path cross-sectional area of the bypass flow path
between the buffer tank and at least one of the supply port and the
collection port.
9. The fluid ejection apparatus according to claim 8, wherein the
buffer tank has a deformable outer wall.
10. The fluid ejection apparatus according to claim 7, further
comprising: a first pump in the circulation path between the supply
port and the first tank, the first pump being configured to send
the fluid from the first tank toward the fluid ejection head; a
second pump in the circulation path between the collection port and
the first tank, the second pump being configured to send fluid from
the fluid ejection head toward the first tank; a pressure sensor
configured to detect pressure of the circulation path; and a
processor configured to adjust fluid output rates of the first pump
and the second pump based on the pressure of the circulation
path.
11. The fluid ejection apparatus according to claim 7, further
comprising: a first pump in the circulation path between the supply
port and the first tank, the first pump being configured to send
the fluid from the first tank toward the fluid ejection head; a
second pump in the circulation path between the collection port and
the first tank, the second pump being configured to send fluid from
the fluid ejection head toward the first tank; a pressure sensor
configured to detect pressure of the bypass flow path; and a
processor configured to adjust fluid output rates of the first pump
and the second pump based on a pressure of the bypass flow path as
detected by the pressure sensor.
12. The fluid ejection apparatus according to claim 7, further
comprising: a cartridge outside of the circulation path fluidly
connected to the first tank, wherein an air chamber of the
cartridge is open to the atmosphere.
13. A fluid ejection apparatus, comprising: a fluid ejection head
having a nozzle; a cartridge to store fluid to be supplied to the
fluid ejection head; a circulation path including a first flow path
portion to provide fluid from the cartridge to a supply port of the
fluid ejection head, and a second flow path portion to return fluid
from a collection port of the fluid ejection head to the cartridge;
a bypass flow path that fluidly connects the supply port to the
collection port outside of the fluid ejection head and the
circulation path; a buffer tank in the bypass flow path; and an
opening/closing valve connected to an air chamber of the buffer
tank and configured to selectively open the air chamber to the
atmosphere.
14. The fluid ejection apparatus according to claim 13, wherein the
buffer tank has a flow path cross-sectional area that is larger
than a flow path cross-sectional area of the bypass flow path
between the buffer tank and at least one of the supply port and the
collection port.
15. The fluid ejection apparatus according to claim 14, wherein the
buffer tank has a deformable outer wall.
16. The fluid ejection apparatus according to claim 13, further
comprising: a first pump in the circulation path between the supply
port and the cartridge, the first pump being configured to send the
fluid from the cartridge toward the fluid ejection head; a second
pump in the circulation path between the collection port and the
cartridge, the second pump being configured to send fluid from the
fluid ejection head toward the cartridge; a pressure sensor
configured to detect pressure of the circulation path; and a
processor configured to adjust fluid output rates of the first pump
and the second pump based on the pressure of the circulation path
as detected by the pressure sensor.
17. The fluid ejection apparatus according to claim 13, further
comprising: a first pump in the circulation path between the supply
port and the cartridge, the first pump being configured to send the
fluid from the cartridge toward the fluid ejection head; a second
pump in the circulation path between the collection port and the
cartridge, the second pump being configured to send fluid from the
fluid ejection head toward the cartridge; a pressure sensor
configured to detect pressure of the bypass flow path; and a
processor configured to adjust fluid output rates of the first pump
and the second pump based on a pressure of the bypass flow path as
detected by the pressure sensor.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2017-183721, filed Sep. 25,
2017, the entire contents of which are incorporated herein by
reference.
FIELD
Embodiments described herein relate generally to a fluid
circulation apparatus and a fluid ejection apparatus.
BACKGROUND
A fluid circulation apparatus for circulating fluid through a fluid
ejection head in a circulation path is known. The fluid ejection
apparatus includes a tank having an air layer upstream of the fluid
ejection head in the circulation path to alleviate fluctuations in
the fluid pressure flowing into the fluid ejection head. Thus
fluctuations in the fluid pressure of a nozzle are reduced.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of an inkjet recording apparatus according to
a first embodiment.
FIG. 2 is an explanatory view of a fluid ejection apparatus
according to the first embodiment.
FIG. 3 is a partial perspective view of the fluid ejection
apparatus.
FIG. 4 is a partial front view of the fluid ejection apparatus.
FIG. 5 is an explanatory view of a fluid ejection head of the fluid
ejection apparatus.
FIG. 6 is an explanatory view of a piezoelectric pump of the fluid
ejection apparatus.
FIG. 7 is a block diagram of a control unit of the fluid ejection
apparatus.
FIG. 8 is a flowchart showing a control method of the fluid
ejection apparatus.
FIG. 9 is an explanatory view of a fluid ejection apparatus
according to another embodiment.
FIG. 10 is an explanatory view showing a configuration of a buffer
device of a fluid ejection apparatus according to another
embodiment.
FIG. 11 is an explanatory view of a buffer device of a fluid
ejection apparatus according to another embodiment.
FIG. 12 is an explanatory view showing a configuration of a buffer
device of a fluid ejection apparatus according to another
embodiment.
FIG. 13 is an explanatory view of a buffer device of a fluid
ejection apparatus according to another embodiment.
DETAILED DESCRIPTION
In general, according to one embodiment, a fluid circulation
apparatus includes a first tank to store fluid to be supplied to a
fluid ejection head, a circulation path including a first flow path
portion to provide fluid from the first tank to a supply port of
the fluid ejection head, and a second flow path portion to return
fluid from a collection port of the fluid ejection head to the
first tank, a bypass flow path that connects the supply port to the
collection port outside of the fluid ejection head, and a buffer
tank in the bypass flow path.
First Embodiment
Hereinafter, an inkjet recording apparatus 1 and a fluid ejection
apparatus 10 according to a first embodiment will be described with
reference to FIGS. 1 to 7. It should be noted that the drawings are
schematic and are drawn with exaggeration and omissions for
purposes of explanatory convenience. In general, components are not
drawn to scale. In addition, the number of components, the
dimensional ratio between different components, or the like, does
not necessarily match between different drawings or to actual
devices. FIG. 1 is a side view of the inkjet recording apparatus 1.
FIG. 2 is an explanatory view of the fluid ejection apparatus 10.
FIGS. 3 and 4 are a partial perspective view and a partial front
view of the configuration of the fluid ejection apparatus 10. FIG.
5 is an explanatory view of a fluid ejection head 20. FIG. 6 is an
explanatory view of a first circulation pump 33, a second
circulation pump 36, and a replenishing pump 53. FIG. 7 is a block
diagram of the fluid ejection apparatus 10.
The inkjet recording apparatus 1 shown in FIG. 1 includes a
plurality of the fluid ejection apparatuses 10, a head support
mechanism 11 for movably supporting the fluid ejection apparatus
10, a medium support mechanism 12 for movably supporting a
recording medium S, and a host control device 13.
As shown in FIG. 1, the plurality of fluid ejection apparatuses 10
is arranged in parallel in a predetermined direction and supported
by the head support mechanism 11. The fluid ejection apparatus 10
integrally includes a fluid ejection head 20 and a circulation
device 30. The fluid ejection apparatus 10 ejects, for example, an
ink I from the fluid ejection head 20 as fluid, thereby forming a
desired image on the recording mediums S arranged opposite to each
other.
The plurality of fluid ejection apparatuses 10 ejects multiple
colors such as a cyan ink, a magenta ink, a yellow ink, a black
ink, and a white ink, respectively, but the color or characteristic
of the ink I to be used is not limited. For example, in place of a
white ink, a transparent glossy ink, a specialty ink that develops
a color when irradiated with infrared rays or ultraviolet rays, or
the like may be ejected. The plurality of fluid ejection
apparatuses 10 have the same configuration although fluid to be
ejected is different.
The fluid ejection head 20 shown in FIGS. 3 to 5 is an inkjet head
and includes a nozzle plate 21 having a plurality of nozzles 21a, a
substrate 22, and a manifold 23 joined to the substrate 22. The
substrate 22 is mounted so as to face the nozzle plate 21 and is
configured in a predetermined shape to form a flow path 28
including a plurality of fluid pressure chambers 25 in between the
substrate 22 and the nozzle plate 21. An actuator 24 is provided on
a portion of the substrate 22 facing each fluid pressure chamber
25. The substrate 22 has partition walls between adjacent fluid
pressure chambers 25 in the same row. The actuator 24 is disposed
to face the nozzle 21a, and the fluid pressure chamber 25 is formed
between the actuator 24 and the nozzle 21a.
The fluid ejection head 20 includes the flow path 28, with the ink
pressure chamber 25 thereon, as formed by the nozzle plate 21, the
substrate 22, and the manifold 23. The actuator 24 having
electrodes 24a and 24b is provided at a portion of the substrate 22
facing the fluid pressure chamber 25. The actuator 24 is connected
to a drive circuit. In the fluid ejection head 20, the actuator 24
deforms according to applied voltages under the control of a module
control unit 38 (depicted in FIG. 2), thereby causing fluid to be
ejected from the opposing nozzle 21a.
As shown in FIGS. 2 to 4, the circulation device 30 is connected
to, or integrated with, the upper part of the fluid ejection head
20 by metal connecting parts. The circulation device 30 includes a
circulation path 31 through which fluid circulates through the
fluid ejection head 20, an intermediate tank 32 provided in the
circulation path 31, the first circulation pump 33, a bypass flow
path 34, a buffer tank 35 (as a buffer device 100), the second
circulation pump 36, a plurality of opening/closing valves 37a and
37b, and the module control unit 38 that controls a fluid ejection
operation. In general, a buffer tank is a buffer device and may be
a discrete component connected to a flow path or may be an integral
portion of the flow path formed or shaped to function as a flow
buffer within the flow path.
The circulation device 30 includes a cartridge 51, functioning as a
supply tank provided outside the circulation path 31, a supply path
52, and the replenishing pump 53. The cartridge 51 is configured to
hold the fluid to be supplied to the intermediate tank 32, and the
internal air chamber of the cartridge 51 is open to the atmosphere.
The supply path 52 is a flow path connecting the intermediate tank
32 and the cartridge 51. The replenishing pump 53 is provided in
the supply path 52 and delivers the fluid from the cartridge 51 to
the intermediate tank 32.
The circulation path 31 includes a first flow path 31a connecting
the intermediate tank 32 and a supply port 20a (of the fluid
ejection head 20) and a second flow path 31b connecting a
collection port 20b (of the fluid ejection head 20) and the
intermediate tank 32. The circulation path 31 passes from the
intermediate tank 32 through the first flow path 31a to the supply
port 20a and passes from the collection port 20b through the second
flow path 31b to the intermediate tank 32. In the first flow path
31a, the first circulation pump 33 is provided. In the second flow
path 31b, the second circulation pump 36 is provided. The first
flow path 31a is provided with a first pressure sensor 39a (also
referred to as a first pressure detector) that detects the fluid
pressure in the first flow path 31a. The second flow path 31b is
provided with a second pressure sensor 39b (also referred to as a
second pressure detector) that detects the fluid pressure in the
second flow path 31b.
The intermediate tank 32 is connected to the fluid ejection head 20
by the circulation path 31 and is configured to store fluid. The
intermediate tank 32 is provided with the opening/closing valve 37a
configured to open the air chamber of the intermediate tank 32 to
the atmosphere. A fluid level sensor 54 is provided to detect the
fluid level in the intermediate tank 32.
The bypass flow path 34 is a flow path that connects the downstream
side of the first circulation pump 33 on the first flow path 31a
and the upstream side of the second circulation pump 36 on the
second flow path. The bypass flow path 34 connects the primary side
of the fluid ejection head 20 and the secondary side of the fluid
ejection head 20 in the circulation path 31 in a short circuiting
manner (that is, without passing through the fluid ejection head
20). The buffer tank 35 is connected to the bypass flow path 34.
That is, the bypass flow path 34 includes a first bypass flow path
34a connecting the buffer tank 35 and the first flow path 31a and a
second bypass flow path 34b connecting the buffer tank 35 and the
second flow path 31b.
For example, the first bypass flow path 34a and the second bypass
flow path 34b may have the same length and the same diameter, both
of which have a smaller diameter than the circulation path 31. For
example, in the first embodiment, the diameter of the circulation
path 31 is set to about 2 to 5 times the diameter of the first
bypass flow path 34a or the second bypass flow path 34b. As an
example, the flow path diameter .phi.1 of the bypass flow path 34
is set to 0.7 mm or less, and the flow path diameter .phi.2 of the
circulation path 31 is set to about 2.0 mm. The first bypass flow
path 34a and the second bypass flow path 34b are each configured to
have a length L1 of about 2 mm.
In the first embodiment, the buffer tank 35 is provided at a
midpoint of the bypass flow path 34. In the circulation path 31,
the distance from a branch point at which the bypass flow path 34
branches from the first flow path 31a to the supply port 20a is the
same as the distance from the collection port 20b to the junction
point of the second bypass flow path 34b.
The buffer tank 35 has a flow path cross-sectional area larger than
the flow path cross-sectional area of the bypass flow path 34 and
is configured to store fluid. The buffer tank 35 has, for example,
an upper wall, a lower wall, a rear wall, a front wall, and a pair
of right and left side walls and is configured to have a
rectangular box shape forming an accommodating chamber 35a for
storing fluid therein. The bypass flow path 34 is connected to
predetermined portions of the lower portion of the pair of side
walls of the buffer tank 35, respectively. In the first embodiment,
for example, the connection position of the first bypass flow path
34a on the inflow side to the buffer tank 35 and the connection
position of the second bypass flow path 34b on the outflow side to
the buffer tank 35 are set to the same height.
The buffer tank 35 has a flow path cross-sectional area 200 times
to 300 times the flow path cross-sectional area of the bypass flow
path 34. For example, the buffer tank 35 is configured such that
the dimensions in a height direction and a depth direction, which
are two directions orthogonal to the bypass flow path 34, are 10
mm, respectively and the dimension in a width direction parallel to
the bypass flow path 34 is about 20 mm.
In the buffer tank 35, the fluid flowing through the bypass flow
path 34 is disposed in the lower region of the accommodating
chamber 35a, and an air chamber is formed in the upper region of
the accommodating chamber 35a. That is, the buffer tank 35 may
store a predetermined amount of fluid and air. By this buffer tank
35, the flow path cross-sectional area of the fluid flowing from
the bypass flow path 34 is enlarged, whereby the accommodating
chamber 35a acts as a spring, and fluctuations in the pressure in
the circulation path 31 are absorbed.
The buffer tank 35 is configured so that the volume of the
accommodating chamber 35a is variable. Specifically, a part of the
wall forming the accommodating chamber 35a (FIG. 4) of the buffer
tank 35 is made of an elastically deformable material. Here, the
front wall forming the accommodating chamber 35a of the buffer tank
35 is composed of a deformable film 35c made of, for example,
polyimide or PTFE.
The opening/closing valve 37b is configured to open the air chamber
of the buffer tank 35 to the atmosphere. That is, a connecting pipe
35d extending upward is provided on the upper wall of the buffer
tank 35, and the opening/closing valve 37b that opens and closes
the flow path in the connecting pipe 35d is provided at the other
end of the connecting pipe 35d.
The circulation path 31, the bypass flow path 34, and the supply
path 52 include a pipe made of a metal or a resin material, and a
tube that covers the outer surface of the pipe, for example, a PTFE
tube.
The first pressure sensor 39a and the second pressure sensor 39b
output pressure as an electric signal using a semiconductor
piezoresistive pressure sensor, for example. The semiconductor
piezoresistive pressure sensor includes a diaphragm that receives
external pressure and a semiconductor strain gauge formed on the
surface of the diaphragm. The semiconductor piezoresistive pressure
sensor detects the pressure by converting the change in the
electrical resistance caused by the piezoresistive effect generated
in the strain gauge as the diaphragm deforms due to the pressure
from the outside into an electric signal.
The fluid level sensor 54 is configured to include a float 55
floating on the fluid surface and moving up and down and Hall ICs
56a and 56b provided at two predetermined positions in the upper
and lower portions. The fluid level sensor 54 detects the amount of
fluid in the intermediate tank 32 by detecting the float 55
reaching an upper limit position and the lower limit position by
the Hall ICs 56a and 56b to send the detected data to the module
control unit 38.
The opening/closing valves 37a and 37b are provided in the
intermediate tank 32 and the buffer tank 35. The opening/closing
valves 37a and 37b are normally closed solenoid opening/closing
valves which are opened when power is turned on and closed when the
power is turned off. The opening/closing valves 37a and 37b are
opened and closed under the control of the module control unit 38,
so that the air chamber of the intermediate tank 32 and the buffer
tank 35 may be opened and closed with respect to the
atmosphere.
The first circulation pump 33 is provided in the first flow path
31a of the circulation path 31. The first circulation pump 33 is
disposed between the primary side of the fluid ejection head 20 and
the intermediate tank 32 and sends fluid toward the fluid ejection
head 20 disposed downstream. The fluid in the first flow path 31a
is distributed to the fluid flowing in the fluid ejection head 20
and the fluid flowing in the buffer tank 35 through the bypass flow
path 34, according to the flow resistance of the flow path through
the fluid ejection head 20 and the flow path through the bypass
flow path 34. In the first embodiment, the bypass flow path 34 has
a smaller diameter than the circulation path 31 so that the flow
path resistance on the bypass flow path 34 side is 2 to 5 times the
flow path resistance on the fluid ejection head 20 side.
The pressure in the circulation path 31 is such that the primary
side of the fluid ejection head 20, that is, the inflow side is at
a higher pressure than the secondary side of the fluid ejection
head 20, that is, the outflow side due to the pressure loss due to
the resistance of the fluid ejection head 20. Therefore, in the
circulation path 31 and the bypass flow path 34 passing through the
fluid ejection head 20, fluid flows from the high-pressure primary
side to the low-pressure secondary side, as indicated by arrows in
FIG. 2.
The second circulation pump 36 is provided in the second flow path
31b of the circulation path 31. The second circulation pump 36 is
disposed between the secondary side of the fluid ejection head 20
and the intermediate tank 32 and sends fluid to the intermediate
tank 32 disposed downstream.
The replenishing pump 53 is provided in the supply path 52. The
replenishing pump 53 sends the ink I held in the cartridge 51
toward the intermediate tank 32.
The first circulation pump 33, the second circulation pump 36, and
the replenishing pump 53 each include a piezoelectric pump 60 as
shown in FIG. 6, for example. The piezoelectric pump 60 includes a
pump chamber 58, a piezoelectric actuator 59 provided in the pump
chamber 58 and vibrating by a voltage, and check valves 61 and 62
disposed at the inlet and outlet of the pump chamber 58. The
piezoelectric actuator 59 is configured to vibrate at a frequency
of, for example, about 50 Hz to 200 Hz. The first circulation pump
33, the second circulation pump 36, and the replenishing pump 53
are connected to the drive circuit by wiring and are configured to
be controllable under the control of the module control unit 38.
When an AC voltage is applied to the piezoelectric pump 60 and the
piezoelectric actuator 59 is operated, the volume of the pump
chamber 58 changes. In the piezoelectric pump 60, when the applied
voltage changes, the maximum change amount of the piezoelectric
actuator 59 changes, and the volume change amount of the pump
chamber 58 changes. Then, when the volume of the pump chamber 58 is
deformed in a direction to increase, the check valve 61 at the
inlet of the pump chamber 58 is opened and the fluid flows into the
pump chamber 58. On the other hand, when the volume of the pump
chamber 58 changes in a direction to decrease, the check valve 62
at the outlet of the pump chamber 58 opens and the fluid flows out
from the pump chamber 58. The piezoelectric pump 60 repeats
expansion and contraction of the pump chamber 58 to deliver the ink
I to the downstream. Therefore, when the voltage applied to the
piezoelectric actuator 59 is large, fluid delivery capability
becomes strong, and when the voltage is small, the fluid delivery
capability becomes weak. For example, in the first embodiment, the
voltage applied to the piezoelectric actuator 59 is varied between
50 V and 150 V.
As shown in FIG. 7, the module control unit 38 includes a CPU 71,
drive circuits 75a to 75e for driving each element, a storage unit
72 that stores various kinds of data, and a communication interface
73 for communication with an externally provided host control
device (host computer) 13 on a control board integrally mounted on
the circulation device 30.
The module control unit 38 communicates with the host control
device 13 in a state of being connected to the host control device
13 through the communication interface 73, thereby receiving
various information such as operation conditions and like.
An input operation by the user and an instruction from the host
control device 13 of the inkjet recording apparatus 1 are
transmitted to the CPU 71 of the module control unit 38 by the
communication interface 73. Various information acquired by the
module control unit 38 is sent to the host control device 13 of the
inkjet recording apparatus 1 via the communication interface
73.
The CPU 71 corresponds to the central part of the module control
unit 38. The CPU 71 controls each unit to realize various functions
of the fluid ejection apparatus 10 according to the operating
system and the application program.
The various pumps 33, 36, and 53 of the circulation device 30, the
drive circuits 75a, 75b, 75c, 75d of the opening/closing valves 37a
and 37b, the various sensors 39a, 39b, 54, and the drive circuit
75e of the fluid ejection head 20 are connected to the CPU 71.
For example, the CPU 71 has a function as circulation means for
circulating the fluid by controlling the operations of the first
and second circulation pumps 33 and 36.
The CPU 71 has a function as replenishing means for replenishing
fluid from the cartridge 51 to the circulation path 31 by
controlling the operation of the replenishing pump 53 based on the
information detected by the fluid level sensor 54 and the pressure
sensors 39a and 39b.
The CPU 71 has a function as a pressure adjustment unit for
adjusting the fluid pressure of the nozzle 21a by controlling the
fluid delivery capability of the first circulation pump 33 and the
second circulation pump 36 based on the information detected by the
first pressure sensor 39a, the second pressure sensor 39b, and the
fluid level sensor 54.
The CPU 71 functions as fluid level adjusting means for adjusting
the fluid level of the intermediate tank 32 and the buffer tank 35
by controlling the opening/closing of the opening/closing valves
37a and 37b.
The storage unit 72 includes, for example, a program memory and a
RAM. The storage unit 72 stores an application program and various
setting values. In the storage unit 72, various setting values such
as a calculation formula for calculating the fluid pressure of the
nozzle 21a, a target pressure range, an adjustment maximum value of
each pump, and the like are stored as control data used for
pressure control, for example.
Hereinafter, a control method of the fluid ejection apparatus 10
according to the first embodiment will be described with reference
to the flowchart of FIG. 8.
In Act 1, the CPU waits for an instruction to start circulation.
For example, when an instruction to start circulation is detected
with a command from the host control device 13 (Yes in Act 1), the
processing proceeds to Act 2. As a printing operation, the host
control device 13 forms an image on the recording medium. S by
performing a fluid ejecting operation while reciprocally moving the
fluid ejection apparatus 10 in a direction orthogonal to the
carrying direction of the recording medium S. Specifically, the CPU
71 carries a carriage 11a (FIG. 1) provided in the head support
mechanism 11 in the direction of the recording medium S to
reciprocally move in the direction of an arrow A. The CPU 71 sends
the image signal corresponding to the image data to the drive
circuit 75e of the fluid ejection head 20, selectively drives the
actuator 24 of the fluid ejection head 20, and ejects droplets of
fluid from the nozzle 21a to the recording medium S.
In Act 2, the CPU 71 drives the first circulation pump 33 and the
second circulation pump 36 to start a fluid circulation operation.
Here, the ink I in the first flow path 31a is distributed to the
fluid flowing in the fluid ejection head 20 and the fluid flowing
in the buffer tank 35 through the bypass flow path 34, according to
the flow resistance of the flow path through the fluid ejection
head 20 and the flow path through the bypass flow path 34. That is,
a part of the ink I flows from the intermediate tank 32 to the
fluid ejection head 20 through the first flow path 31a, passes
through the second flow path 31b, and flows into the intermediate
tank 32 again. The remaining part of the ink I passes through the
bypass flow path 34 and the buffer tank 35 from the first flow path
31a, is sent to the second flow path 31b without passing through
the fluid ejection head 20, and flows into the intermediate tank 32
again. By this circulation operation, the impurities contained in
the ink I are removed by the filter provided in the circulation
path 31.
In Act 3, the CPU 71 opens the opening/closing valve 37a of the
intermediate tank 32 and opens the intermediate tank 32 to the
atmosphere. Since the intermediate tank 32 is open to the
atmosphere and constantly has a constant pressure, pressure drop in
the circulation path due to fluid consumption of the fluid ejection
head 20 is prevented. Here, when the opening/closing valve 37a is
opened for a long time to an extent that there is concern about
temperature rise of the opening/closing valve 37a, the
opening/closing valve 37a may be opened periodically for a short
time. Even if the opening/closing valve 37a is closed, it is
possible to keep the fluid pressure of the nozzle constant unless
the circulation path is excessively reduced in pressure. The
solenoid type opening/closing valve 37a is normally closed.
Therefore, even if the power supply to the apparatus suddenly stops
due to a power failure or the like, the opening/closing valve 37a
may shut off the intermediate tank 32 from the atmospheric pressure
by being closed instantaneously and seal the circulation path 31.
Therefore, it is possible to suppress leakage of the ink I from the
nozzle 21a of the fluid ejection head 20.
At the timing instructed by the host control device 13, the CPU 71
opens the opening/closing valve 37b of the buffer tank 35 and opens
the buffer tank 35 to the atmosphere. Since the buffer tank 35 is
opened to the atmosphere and has atmospheric pressure, the fluid
level of the buffer tank 35 is lowered.
In this fluid circulation operation, the pressure fluctuation
accompanying the ejection operation of the fluid or the like is
absorbed by the volume change of the buffer tank 35 and the spring
action of the air of the accommodating chamber 35a, and the
pressure variation is alleviated.
In Act 4, the CPU 71 detects the pressure data transmitted from the
first pressure sensor 39a. The CPU 71 detects the fluid level of
the intermediate tank 32 based on the data transmitted from the
fluid level sensor 54.
In Act 5, the CPU 71 starts fluid level adjustment. Specifically,
the CPU 71 drives the replenishing pump 53 based on the detection
results of the fluid level sensor 54, thereby performing fluid
replenishment from the cartridge 51 and adjusting the fluid level
position to an appropriate range. For example, at the time of
printing, the ink I is ejected from the nozzle 21a, the fluid
amount of the intermediate tank 32 instantaneously decreases, and
when the fluid level is lowered, the fluid is replenished. When the
fluid amount increases again and the output of the fluid level
sensor 54 is inverted, the CPU 71 stops the replenishing pump
53.
In Act 6, the CPU 71 detects the fluid pressure of the nozzle from
the pressure data. Specifically, the fluid pressure of the nozzle
21a is calculated by using a predetermined arithmetic expression
based on the pressure data on the upstream side and the downstream
side transmitted from the first and second pressure sensors 39a and
39b.
For example, it is possible to obtain a fluid pressure Pn of the
nozzle by adding a pressure .mu.gh generated by the water head
difference between the height of the pressure measurement point and
the head height of the nozzle surface height to the average value
of a fluid pressure value Ph of the first flow path 31a and a fluid
pressure value P1 of the second flow path 31b. Here, it is assumed
that .rho. is a density of the fluid, g is gravitational
acceleration, and h is a distance between the pressure measurement
point and the height direction of the nozzle surface.
As the pressure adjustment processing, the CPU 71 calculates a
drive voltage based on the fluid pressure Pn of the nozzle
calculated from the pressure data. Then, the CPU 71 maintains a
negative pressure to an extent that the ink I does not leak from
the nozzle 21a of the fluid ejection head 20 and bubbles are not
sucked from the nozzle 21a and maintains a meniscus Me (FIG. 5) by
driving the first circulation pump 33 and the second circulation
pump 36 so that the fluid pressure Pn of the nozzle becomes an
appropriate value. Here, as an example, it is assumed that the
upper limit of a target value is P1H and the lower limit is
P1L.
In Act 7, the CPU 71 determines whether the fluid pressure Pn of
the nozzle 21a is within an appropriate range, that is, whether
P1L.ltoreq.Pn.ltoreq.P1H. If Pn is out of the appropriate range (No
in Act 7), the CPU 71 determines whether or not the fluid pressure
Pn of the nozzle 21a exceeds the upper limit of the target value
P1H as Act 8.
The fluid pressure at the nozzle 21a of the fluid ejection head 20
is pressurized when the driving of the first circulation pump 33 is
relatively strong, and is depressurized when the driving of the
second circulation pump 36 is relatively strong.
The CPU 71 further determines whether or not the drive voltage is
within the adjustment range of the first circulation pump 33 and
the second circulation pump 36 (Acts 9 and 12) and pressurizes or
depressurizes by using the first circulation pump 33 and the second
circulation pump 36 when the drive voltage exceeds an adjustment
maximum value Vmax of the first and second circulation pumps 33 and
36.
More specifically, when the fluid pressure Pn of the nozzle 21a is
out of the appropriate range (No in Act 7) and the fluid pressure
Pn of the nozzle 21a does not exceed the target value upper limit
P1H (No in Act 8), that is, when the fluid pressure Pn of the
nozzle is lower than the target lower limit P1L, the CPU 71
determines whether or not a drive voltage V+ of the pressurizing
side first circulation pump 33 is equal to or higher than the
adjustment maximum value Vmax, that is, whether or not the drive
voltage V+ exceeds the adjustable range of the first circulation
pump 33 as Act 9. When the drive voltage V+ of the pressurizing
side first circulation pump 33 is equal to or higher than the
adjustment maximum value Vmax (Yes in Act 9), the CPU 71
pressurizes the voltage by lowering the voltage of the second
circulation pump 36 as Act 10. On the other hand, if the drive
voltage V+ of the first circulation pump on the pressurizing side
is lower than the adjustment maximum value Vmax, and within the
adjustable range (No in Act 9), the CPU 71 pressurizes the voltage
by increasing the drive voltage of the first circulation pump 33 as
Act 11.
In Act 8, when the fluid pressure Pn of the nozzle exceeds the
target value upper limit P1H (Yes in Act 8), the CPU 71 determines
whether or not a drive voltage V- of the second circulation pump 36
on the depressurizing side is equal to or higher than the
adjustment maximum value Vmax, that is, whether or not the drive
voltage V- exceeds the adjustment range of the second circulation
pump 36 as Act 12. When the drive voltage V- of the second
circulation pump 36 on the depressurizing side is equal to or
higher than the adjustment maximum value Vmax (Yes in Act 12), the
CPU 71 depressurizes the voltage by lowering the voltage of the
first circulation pump 33 as Act 13. On the other hand, if the
drive voltage V- of the second circulation pump 36 on the
depressurizing side is lower than the adjustment maximum value
Vmax, and within the adjustable range (No in Act 12), the CPU 71
depressurizes the voltage by decreasing the drive voltage of the
second circulation pump 36 as Act 14. That is, the CPU 71 performs
pressure adjustment in Acts 7 to 14.
If Pn of the fluid pressure of the nozzle plate 21 is within the
appropriate range (Yes in Act 7), the CPU 71 proceeds to Act 15.
The CPU 71 performs feedback control of Acts 4 to 14 until a
circulation end command is detected in Act 15. Then, when detecting
an instruction to end the circulation with a command from the host
control device 13 (Yes in Act 15), the CPU 71 closes the
opening/closing valve 37a of the intermediate tank 32 and seals the
intermediate tank 32 (Act 16). The CPU stops the first circulation
pump 33 and the second circulation pump 36 and ends the circulation
processing (Act 17).
The fluid ejection apparatus 10 configured as described above may
stabilize the ejection performance of the fluid ejection head 20 by
connecting the flow paths on the upstream side and the downstream
side of the fluid ejection head 20 with the bypass flow path 34 and
providing the buffer tank 35. That is, by connecting the flow paths
on the upstream side and the downstream side of the fluid ejection
head 20 with the bypass flow path 34 and disposing the buffer tank
35 and the fluid ejection head 20 in parallel, due to the change in
the flow path cross-sectional area between the bypass flow path 34
and the buffer tank 35 and the action of an air layer in the buffer
tank 35 as an air spring, the pressure fluctuation in the bypass
flow path 34 is absorbed and the pulsation is absorbed, thereby
stabilizing the ejection performance.
For example, when the circulation path 31 becomes negative pressure
due to a large amount of fluid ejection, the volume of the buffer
tank 35 is reduced and the fluid level of the buffer tank 35 is
lowered so that the pressure fluctuation on the circulation path 31
side may be absorbed.
The bypass flow path 34 is configured to flow fluid without passing
through the fluid ejection head 20. Therefore, for example, if the
pressure of the bypass flow path 34 is greatly decreased, the fluid
level in the buffer tank 35 is lowered. Even if air bubbles are
mixed, since the bubbles in the buffer tank 35 are sent to the
intermediate tank 32 through the second bypass flow path 34b on the
downstream side without passing through the fluid ejection head 20,
the air bubbles may be removed and the ejection performance is not
affected.
The fluid ejection apparatus 10 may stabilize the fluid level of
the buffer tank 35 at all times because the buffer tank 35 is
configured to be openable to the atmosphere. In the fluid ejection
apparatus 10, a part of the buffer tank 35 is made of a material
which may be elastically deformable, and the volume is variable,
thereby ensuring the absorption amount of the pressure
fluctuation.
The fluid ejection apparatus 10 appropriately sets the pipe
resistance of the bypass flow path 34, thereby appropriately
maintaining the flow rate of the fluid passing through the fluid
ejection head 20 and the fluid flowing through the bypass flow path
34.
The fluid ejection apparatus 10 may maintain the fluid pressure of
the nozzle properly by detecting the pressure on both the upstream
side and the downstream side of the fluid ejection head 20 and
performing feedback control of the pressure with the first
circulation pump 33 and the second circulation pump 36 that
pressurize. Therefore, even when the pump performance changes over
time, it is possible to realize appropriate pressure control.
In the fluid ejection apparatus 10, since the piezoelectric pump 60
is used as the first circulation pumps 33 and 36, the configuration
is simple and material selection is easy. That is, the
piezoelectric pump 60 does not require a large drive source such as
a motor, a solenoid, and the like and may be made smaller than a
general diaphragm pump, a piston pump, and a tube pump. For
example, if a tube pump is used, there is a possibility that the
tube and the fluid come into contact with each other, and therefore
it is necessary to select a material that does not cause
deterioration of the tube or fluid. On the other hand, it is easy
to select a material by using piezoelectric pump 60. For example,
in the first embodiment, the fluid contact parts of the
piezoelectric pump 60 may be made of SUS 316 L, PPS, PPA, and
polyimide which are excellent in chemical resistance.
In the first embodiment, by using the first circulation pump 33 on
the upstream side which may be pressurized when the voltage is
increased and depressurized when the voltage is lowered, and the
second circulation pump 36 on the downstream side which may be
depressurized when the voltage is increased and pressurized when
the voltage is lowered, when the drive voltage exceeds the
adjustable range, another pump may be used, thereby realizing
highly accurate control. The functions required for controlling the
first circulation pump 33, the second circulation pump 36, the
replenishing pump 53, the first and second pressure sensors 39a,
39b, the fluid level sensor 54, the control board 70, and other
fluid supply, circulation, and pressure adjustment are concentrated
in the circulation device 30. Therefore, as compared with a
large-sized stationary type circulation device, it is possible to
simplify the connection and the electrical connection between the
main body of the inkjet recording apparatus 1 and the carriage 11a.
As a result, the inkjet recording apparatus 1 may be reduced in
size, weight, and cost.
Second Embodiment
Hereinafter, a fluid ejection apparatus 10A according to a second
embodiment will be described with reference to FIG. 9. FIG. 9 is an
explanatory view of the fluid ejection apparatus 10A. The fluid
ejection apparatus 10A according to the second embodiment is the
same as the fluid ejection apparatus 10 according to the first
embodiment except that the cartridge 51 is used as the intermediate
tank 32. The same reference numerals are used for the components
that are substantially the same as those of the first embodiment,
and the description of repeated components may be omitted.
As shown in FIG. 9, in the fluid ejection apparatus 10A according
to the second embodiment, as the intermediate tank 32, the
intermediate tank 32 that is openable to the atmosphere is disposed
in the circulation path 31 between the first flow path 31a and the
second flow path 31b. That is, the cartridge 51 in the fluid
ejection apparatus 10 is used as the intermediate tank 32. The
opening/closing valve 37a may control opening/closing of the
intermediate tank 32 with respect to the atmosphere, or the
intermediate tank 32 may be always opened to the atmosphere. In the
second embodiment, the same effect as in the first embodiment may
be obtained. The cartridge 51 is used as the intermediate tank 32,
and the configuration thereof may be omitted. In a fluid
circulation apparatus and a fluid ejection apparatus having the
above structure, the same effect as in the first embodiment may be
obtained.
The configuration of the fluid ejection apparatus according to the
example embodiments described above is not limited.
For example, the connection positions to the buffer tank 35 are set
to the same height, but a height of the connection positions is not
limited thereto. For example, the outflow port of the buffer tank
35 may be disposed above the inflow port. In this case, it is easy
to guide the bubbles to the outflow side, and it is possible to
promote discharge of bubbles.
The structure of the buffer device is not limited to those in the
example embodiments described above. For example, in the example
embodiments described above, the buffer tank 35, as a buffer device
has a rectangular parallelepiped box. However, in some embodiments,
a buffer device 101 depicted in FIG. 10 may include a buffer tank
135 in which the flow path diameter gradually expands and contracts
and an inner wall is formed in a curved surface shape. Even in this
case, due to the change in the flow path cross-sectional area and
the action of the air layer of the accommodating chamber 135a as an
air spring, it is possible to obtain an effect of stabilizing the
ejection performance by absorbing the pressure fluctuation in the
bypass flow path 34 and absorbing the pulsation.
In some embodiments, the buffer device 102 depicted in FIG. 11 may
include a plurality of buffer tanks 235 having a flow path
cross-sectional areas enlarged in the bypass flow path 34. The
plurality of buffer tanks 235 is disposed in series in the bypass
flow path 34. That is, the bypass flow path 34 changes the
cross-sectional area thereof so as to repeatedly expand and
contract the flow path cross-sectional area multiple times. Even in
this case, due to the change in the flow path cross-sectional area
and the action of the air layer of an accommodating chamber 235a as
an air spring, it is possible to obtain an effect of stabilizing
the ejection performance by absorbing the pressure fluctuation in
the bypass flow path 34 and absorbing the pulsation.
In some embodiments, the buffer device 103 depicted in FIG. 12 may
be replaced with the buffer tank 35 in which the pipe wall of the
bypass flow path 34 is formed of an elastically deformable material
such as thin polyimide, thin PTFE or the like, and include a
chamber 335 that constitutes an air chamber 335a on the outer
periphery of the bypass flow path 34. That is, the buffer device
103 surrounds the deformable bypass flow path 34 with the air
chamber 335a. Even in this case, by forming the pipe wall of the
bypass flow path 34 with an elastically deformable material, due to
the change in the flow path cross-sectional area and the action of
the air layer of the air chamber 335a as an air spring, it is
possible to obtain an effect of stabilizing the ejection
performance by absorbing the pressure fluctuation in the bypass
flow path 34 and absorbing the pulsation.
It is also possible to add elements such as a distributing plate or
an impeller in the buffer tank 35. In some embodiments, the buffer
device 104 depicted in FIG. 13 may include a distributing plate
inside the buffer tank 35 in which the flow path cross-sectional
area is enlarged. Even in this case, due to the change in the flow
path cross-sectional area of the bypass flow path 34 and the action
of the air layer of an accommodating chamber 35a as an air spring,
it is possible to obtain an effect of stabilizing the ejection
performance by absorbing the pressure fluctuation in the bypass
flow path 34 and absorbing the pulsation.
In the example embodiments described above, the flow path diameter
of the bypass flow path 34 is smaller than the flow path diameter
of the circulation path 31 which is the mainstream and the flow
path resistance on the bypass flow path 34 side is increased.
However, the flow path diameter of the bypass flow path 34 is not
limited thereto. For example, when the flow rate may be secured, it
is also possible to reduce the flow resistance on the bypass flow
path 34 side by making the diameter of the bypass flow path 34
larger than the diameter of the circulation path 31.
Here, the operation principle will be described. In FIG. 2, the
pressure of the supply port 20a of the first bypass flow path 34a
and the fluid ejection head 20 is the same. The pressure of the
collection port 20b of the second bypass flow path 34b and the
fluid ejection head 20 is the same. If the diameter of the bypass
flow path 34 is made larger than the diameter of the circulation
path 31, the amount of fluid flowing into the bypass flow path 34
and the buffer tank 35 is larger than the amount of fluid flowing
in the fluid ejection head 20. Then, the pressure of the bypass
flow path 34 having a large amount of flowing fluid determines the
pressure of the supply port 20a of the fluid ejection head 20 and
the pressure of the collection port 20b of the fluid ejection head
20 more predominantly. Therefore, the pressure of the fluid
ejection head 20 will be influenced more by the pressure of the
bypass flow path 34. The pressure fluctuation is absorbed by the
change in the flow path cross-sectional area between the bypass
flow path 34 and the buffer tank 35 and the action of the air layer
in the buffer tank 35 as an air spring and is influenced more by
the pressure of the bypass flow path 34 whose pulsation is
absorbed, whereby the pulsation of the fluid ejection head 20 may
be reduced, and the ejection performance is stabilized.
The fluid ejection apparatuses 10 and 10A may also eject fluid
other than ink. As a fluid ejection apparatus that ejects fluid
other than ink, for example, an apparatus that ejects fluid
containing conductive particles for forming a wiring pattern of a
printed wiring board, or the like may be used.
In some embodiments, the fluid ejection head 20 may have a
structure in which droplets of fluid are ejected by deforming the
diaphragm with static electricity, a structure in which droplets of
fluid are ejected from a nozzle using thermal energy of a heater,
or the like.
In the example embodiments described above, the fluid ejection
apparatus is used for the inkjet recording apparatus 1. However,
the use of the fluid apparatus is not limited to this example. The
fluid ejection apparatus may also be used, for example, in 3D
printers, industrial manufacturing machines, and medical
applications and may be reduced in size, weight, and cost.
As the first circulation pump 33, the second circulation pump 36,
and the replenishing pump 53, for example, a tube pump, a diaphragm
pump, a piston pump or the like may be used instead of the
piezoelectric pump 60.
In the example embodiments described above, the circulation pumps
33 and 36 are provided on the upstream side and the downstream
side, respectively. However, a single circulation pump may be used.
Even in this case, it is possible to perform the same function as
in the above embodiment by adjusting the positive and negative
pressure states of the circulation path by pushing and pulling the
fluid.
In the example embodiments described above, the first pressure
sensor 39a that detects the fluid pressure in the first flow path
31a is provided in the first flow path 31a and the second pressure
sensor 39b that detects the fluid pressure in the second flow path
31b is provided in the second flow path 31b. However, a single
pressure sensor may be used in these examples.
While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to
limit the scope of the present disclosure. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms. Furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the disclosure. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
present disclosure.
* * * * *